Bios at latest version. Drivers updated.
PSU replaced, ram swapped. Going to reinstall OS anyway.
When it crashes there's no BSoD, no errors generated, and sometimes but not always the bios reverts to factory defaults. Since I don't run OC on this (not even XMP) it only affects the fan curves.
I've stress tested under memtest86+, fuzzy donut, intel burnintest, each for at least 24h, no replicatable crashes. It's totally random. We've gone through everything our friend from Intel can suggest as well as Dr. Professor Beardasaur (and everyone on his stream) - general concensus is we're down to either CPU or MB. The only things that haven't been validated are CPU/MB/OS - and afaik (feel free to correct if wrong) OS crashes 1) generally create errors and 2) don't force factory defaults on MB.